Glossa Ordinaria — as excerpted in the Catena Aurea on Matthew 26:26

“(non occ.) Thise we must understand to be wheat bread, for the Lord compared Himself to a grain of wheat, saying, Except a corn fall into the ground &c. Such bread also is suitable for the Sacrament, because it is in common use; bread of other kinds being only made when this fails. But for as much as Christ up to the very last day, to use the words of Chrysostom as above, (p. 886.) shewed that He did nothing contrary to the Law, and the Law commanded that unleavened bread should be eaten in the evening when the Passover was slain, and that all leavened should be put away, it is manifest that the bread which the Lord took and gave to His disciples was unleavened.”